Power supply considerations

RHF330

12/22

Doc ID 15576 Rev 3

4

Power supply considerations

Correct power supply bypassing is very important for optimizing performance in high-

frequency ranges. The bypass capacitors should be placed as close as possible to the IC

pins to improve high-frequency bypassing. A capacitor greater than 1

μF is necessary to

minimize the distortion. For better quality bypassing, a 10 nF capacitor can be added. It

should also be placed as close as possible to the IC pins. The bypass capacitors must be

incorporated for both the negative and the positive supply.

For example, on the RHF3xx single op-amp demonstration board, these capacitors are C6,

C7, C8, C9.

Figure 28.

Circuit for power supply bypassing

4.1

Single power supply

In the event that a single supply system is used, biasing is necessary to obtain a positive

DC component of the signal at this value. Several options are possible to provide this bias

supply, such as a virtual ground using an operational amplifier or a two-resistance divider

(which is the cheapest solution). A high resistance value is required to limit the current

consumption. On the other hand, the current must be high enough to bias the non-inverting

input of the amplifier. If we consider this bias current (55

μA maximum) as 1% of the current

through the resistance divider, to keep a stable mid-supply, two resistances of 470

Ω can be

used.

The input provides a high-pass filter with a break frequency below 10 Hz which is necessary

Figure 29 on page 13 illustrates a 5 V single power supply configuration for the RHF3xx

single op-amp demonstration board.

+

+V

CC

10 µF

+

10 nF

10 µF

+

10 nF

-

-V

CC

AM00835